Direct positive processing of silver halide with metal dopants in diffusion transfer films

ABSTRACT

Improved processes are disclosed for obtaining positive images in an unfogged, silver halide emulsion wherein a photographic element comprising a support and said emulsion are imagewiseexposed and then either (1) developed in a surface developer in the presence of a silver halide fogging agent or (2) given a light flash during development in a surface developer. In one aspect, the silver halide emulsions of this invention are internal-image emulsions comprising silver halide grains which preferably have metal dopants occluded therein and wherein said grains have been chemically sensitized on the surface thereof to a level less than that which would provide a substantial density in Kodak Developer DK-50 after an imagewise exposure when said emulsions are coated at a coverage of between 300 to 400 mg. of silver/ft.2.

llnited States Patent 1 Evans 1 1 Dec. 2, 1975 1 i DIRECT POSITIVEPROCESSING OF 3.761.276 9/1973 Evans 96/64 SILVER HALIDE WITH METALDOPANTS 3.850.637 11/1974 Evans 96/64 IN DIFFUSION TRANSFER FILMS [75]Inventor: Francis John Evans, Rochester,

[73] Assignee: Eastman Kodak Company,

Rochester, NY.

[22] Filed: Aug. 9, 1974 [21] Appl. No.: 496,433

Related U.S. Application Data [60] Continuation-impart of Ser. No.324,611. Jan. 18, 1973, abandoned, which is a division of Ser. No.123,005, March 10, 1971, Pat. No. 3.761.276.

[52] US. Cl 96/29 D; 96/3; 96/29 R; 96/64; 96/73; 96/74; 96/76 R; 96/77;96/107; 96/108 [51] Int. Cl. G03C 7/00; GO3C 5/54; GOBC 5/24; 603C 1/40[58] Field of Search 96/3, 29 D, 77, 76 R, 64, 96/107. '73, 108,74

[56] References Cited UNITED STATES PATENTS 3,761,267 9/1973 Gilman etal. 96/64 Primary Examiner-Charles L. Bowers, Jr. AssistantExaminer-Richard L. Schilling Attorney, Agent, or Firm-C. 0. Thomas 157] ABSTRACT lmproved processes are disclosed for obtaining positiveimages in an unfogged, silver halide emulsion wherein a photographicelement comprising a support and said emulsion are imagewise=exposed andthen either (1) developed in a surface developer in the presence of asilver halide fogging agent or (2) given a light flash duringdevelopment in a surface developer. In one aspect, the silver halideemulsions of this invention are internal-image emulsions comprisingsilver halide grains which preferably have metal dopants occludedtherein and wherein said grains have been chemically sensitized on thesurface thereof to a level less than that which would provide asubstantial density in Kodak Developer DK-SO after an imagewise exposurewhen said emulsions are coated at a coverage of between 300 to 400 mg.of silver/ft".

23 Claims, N0 Drawings DIRECT POSITIVE PROCESSING OF SILVER HALIDE WITHMETAL DOPANTS IN DIFFUSION TRANSFER FILMS This application is acontinuation-in-part of US. Ser. No, 324,611 filed Jan. 18, 1973 nowabandoned, which in turn is a divisional application of Ser. No.123,005, filed Mar. 10, 1971 now US. Pat. No. 3,761,276 issued Sept. 25,1973. i

This invention relates to unfogged silver halide emulsions and methodsfor forming positive images in unfogged silver halide emulsions. In oneaspect, this invention relates to silver halide emulsions comprisingunfogged silver halide grains having metal dopants occluded therein,said grains having been chemically sensitized on the surface to a levelless than that which will produce substantial density (i.e., Dmax ofless than 0.25) in a surface developer after an imagewise exposure tolight. In another aspect, this invention relates to an improved methodfor obtaining positive images wherein a silver halide element comprisingthe emulsion as described next above is imagewise-exposed and then thesilver halide element is either developed in a surface developer in thepresence of a fogging agent or given a light flash during development.

Processes are known in the art for making positive images in unfoggedsilver halide emulsions by imagewise images exposure followed by foggingdevelopers, etc. Typical processes of this type are disclosed in US.Pat. No. 2,497,875 by Falleson issued Feb. 21, 1950, US. Pat. No.2,588,982 by Ives issued Mar. 11, 1952, and US. Pat. No. 2,456,953 byKnott and Stevens issued Dec. 21, 1948, British Pat. Specification No.1,151,363, and Japanese Pat. No. 29,405/68 issued Dec. 17, 1968.Generally, the prior processes used internal-image silver halideemulsions such as emulsions made by the conversion technique of Daveyand Knott, US. Pat. No. 2,592,250, emulsions made by the techniquesdisclosed in British Pat. Specification No. 1,011,062, and the like. Theemulsion could be used to make positive images by the above techniques,but improved photographic characteristics such as higher photographicspeed, lower Dmin, higher Dmax and the like are desired to obtainacceptance of this system in many applications of photography.

I have now found that silver halide emulsions containing silver halidegrains having metal dopants occluded therein, and wherein said grainshave been chemically sensitized on the surface thereof to a level lessthan that which would provide a substantial density in Kodak DeveloperDK-50 after imagewise exposure, can be imagewise-exposed and processedin a surface developer in the presence ofa fogging agent or by lightfogging during development in a surface developer to provide highlyimproved positive images. This discovery was quite unexpected since oneskilled in the art generally avoided conditions or steps where thesurface of the emulsion would be chemically sensitized before theimagewise exposure when it was to be used in this process to form adirect-positive image. One attempt to solve this problem was tosensitize the surface chemically after imagewise exposure as disclosedin Ridgway, British Pat. Specification No. 1,178,683. However, I havenow found that, when the doped emulsions are used to make positiveimages by this process, a certain amount of surface sensitivity beforeimagewise exposure is very desirable to produce high-quality positiveimages. i

In one embodiment of this invention, an improved process is provided formaking reversal images, the im' provement comprising using an unfoggedsilver halide emulsion containing silver halide grains having metaldopants occluded therein wherein said silver halide grains have beenchemically sensitized to a level which would produce a density of lessthan 0.4 and preferably less than about 0.25 when imagewise-exposed anddeveloped in Kodak Developer DK-50 and to at least a level which wouldprovide a density of 0.5 in an undoped silver halide emulsion of thesame grain size and halide composition when exposed and developed inKodak Developer DK-50, provided said emulsions are coated at a coverageof between 300 to about 400 mg. of Ag/ftF.

As a highly preferred embodiment according to this invention, the usefulsilver halide emulsions can be characterized as being a silver halidecomposition wherein (1) the halide is predominantly bromide, (2) theemulsion comprises grains having metal dopants occluded therein, (3) theemulsions when coated on a film support at a coverage between about 300to 400 mg. Aglftf, imagewise-exposed to a 500watt tungsten lamp for H to1 sec. at a distance of 24 in. and processed in a surface developer suchas 5 min. in Kodak Developer DK-50 will have a Dmax of less than 0.25,and (4) when the emulsions are coated and exposed as described as nextabove and then processed in a fogging developer as described in Ives,US. Pat. No. 2,563,785, the emulsion will have a AD or (Dmax- Dmin) ofgreater than 1.0.

In one preferred embodiment, the emulsions having the characteristicsnext above are processed after imagewise exposure in a silver halidesurface developer in the presence of a hydrazine fogging agent.

In another preferred embodiment, the emulsions having thecharacteristics above are processed after imagewise exposure in a silverhalide surface developer in the presence of a reactive N-substituted,cycloammonium quaternary salt.

In still another embodiment, the silver halide emulsions of thisinvention are processed after imagewise exposure with an overall lightflash during development in a silver halide surface developer, forexample, as disclosed in Knott and Stevens, US. Pat. No. 2,456,953.

In another preferred embodiment, the emulsions of this invention can beused to provide improved directpositive image-transfer systems andprocesses for forming a transfer image. The emulsions of this inventioncan comprise at least one layer in an image-transfer film unit whichadditionally comprises an image-receiving layer and a processingcomposition which can be discharged to facilitate development of thesilver halide emulsion by passing the unit through a pair of juxtaposedpressure-applying members. Preferably, a selective fogging agent islocated in the film unit whereby it will contact said silver halide upondischarge of the processing composition, such as in one layer of theelement or in a rupturable pod. Generally, the internalimage silverhalide emulsions of my invention comprise those wherein the halide ispredominantly bromide and which have a predominant amount of lightsensitivity internal to the silver halide grain and when examinedaccording to normal photographic testing techniques by coating a testportion of the emulsion on a transparent support, exposing to alight-intensity scale for a fixed time between 1 X 10 and 1 sec., anddeveloping for about 5 min. at 65 F. in Developer Y below (aninternal-type developer), have a maximum density at least five times themaximum density of an identical test portion which has been exposed inthe same way and developed for 6 min. at 68 F. in Developer X below (asurface-type developer). Preferably, the maximum density in Developer Yis at least 0.5 density unit greater than the maximum density inDeveloper X and/or the grains of said emulsion have a ratio of totalsensitivity to surface sensitivity of greater than 5.

Developer X N-methyl-p-aminophenol sulfate 2.5 g ascorbic acid 100 gpotassium metaborate 35.0 g potassium bromide 1.0 g water to 1 liter pHof 9.6

Developer Y N-methyl-p-aminophenol sulfate 20 g sodium sulfite,desiccated 90.0 g hydroquinone 8.0 g sodium carbonate, monohydrate 52.5g potassium bromide 5.0 g potassium iodide 0.5 g

water to I liter Internal-image emulsions which are useful according tothis invention are those which contain grains having a metal dopantoccluded therein. The metal dopants can be occluded within the grain,for example, by precipitating in the presence of foreign metal ions(i.e., other than silver ions), occluding metallic compounds within thegrain, etc. The metal dopants can be introduced by chemicallysensitizing a core ofa silver halide grain to form a metal or metal saltthereon and then forming a shell or outer region on the core occludingthe chemically sensitized site within the grain, etc. Typical usefulsilver halide emulsions containing grains having metal dopants occludedtherein can be prepared by the procedures disclosed in U.S. Pat. No.3,206,313 by Porter et al issued Sept. 14, 1965; U.S. Pat. No. 3,317,322by Porter et al issued May 2, 1967; U.S. Pat. No. 3,367,778 by Berrimanissued Feb. 6, 1968, omitting the surface fogging procedure; U.S. Pat.No. 3,447,927 by Bacon et al issued June 3, 1969; U.S. Pat. No.3,531,291 by Bacon et al issued Sept. 29, 1970; U.S. Pat. No. 3,271,157by McBride issued Sept. 6, 1966; and U.S. Pat. No. 3,703,584 by Motter;and British Pat. Specification Nos. 1,027,146 and 1,151,782; and thelike.

The silver halides used in the present invention are unfogged. Suchemulsions contain only minimal developable surface latent images whereinprocessing for min. at 27 C. in Kodak Developer DK-SO will provide adensity of less than 0.4.

Generally, the internal-image emulsions useful in this inventioncomprise silver halide grains having chemical or physical sites internalto the grain for the deposition of photolytic silver. The physical sitescan be obtained by employing precipitation conditions which will resultin the formation of physical defects in the crystal lattice such as, forexample, changing the conditions of the precipitation medium to promotea change in crystal shape, interrupted precipitations, and the like. Thechemical sites can be obtained by incorporating foreign metal dopantsinto the silver halide grain. In certain preferred embodiments, thedopant is a foreign metal ion or a metallic compound. It is understood,of course, that foreign metal ion means an ion other than a silver ion,and that "metallic dopants can include oc- 4 eluded metallic silver,sulfur, sulfur compounds, metallic iridium, metallic gold, metallicplatinum, etc. In certain embodiments, the silver halide grainscontaining occluded metallic compounds can be obtained by precipitatingin the presence of the metallic compound or preferably depositing themetal on a core of silver halide and then continuing formation of thegrain to build a shell or outer region over the metallic deposit.Typical emulsions of this type are disclosed in Porter et al, U.S. Pat.Nos. 3,206,313 and 3,317,322. In one preferred embodiment wherein thesilver halide grains contain occluded metal dopants, the silver halidegrains comprise occluded sulfur and noble metal compounds.

In a preferred embodiment, the silver halide grains are formed in thepresence of foreign metal ions and preferably polyvalent metal ions.Generally, when the grains are formed in an aqueous medium, the silverhalide grains are formed in the presence of the water-soluble salts ofthe respective metal, preferably in an acidic medium. Typicaluseful-polyvalent metal ions include divalent metal ions such as leadions, trivalent metal ions such as antimony, bismuth, arsenic, gold,iridium, rhodium and the like and tetravalent metal ions such asplatinum, osmium, iridium and the like. In highly preferred embodiments,the grains are formed in the presence of bismuth, lead or iridium ions.Generally, the silver halide grains contain at least 10 and preferablyat least 10 mole percent dopant based on silver halide.

The surface of the grains of the doped emulsions of this invention isgenerally chemically sensitized to a level below that which wouldproduce substantial density (i.e., a density of less than 0.4) in asurface developer such as Kodak Developer DK-SO after exposure whencoated at a coverage of between about 300 to 400 mg. Ag/ftF. By chemicalsensitization, I mean sensitization of the type described by AntoineI-Iautot and Henri Saubenier in Science et Industries Photographiques,Vol. XXVIII, January, 1957, pp. l-23, and January, 1957, pp. 57-65. Suchchemical sensitization includes three major classes, viz., gold ornoble-metal sensitization, sulfur sensitization such as by a labilesulfur compound, and reduction sensitization, i.e., treatment of thesilver halide with a strong reducing agent which does not fogappreciably the silver halide, but introduces small specks of metallicsilver into the silver halide crystal or grain. In highly preferredembodiments of this invention, I have found that higher amounts ofsurface sensitivity are desirable in producing good reversal images whenthe silver halide emulsion comprises silver halide grains having metaldopants occluded therein, and especially when the grains containpolyvalent metal ions occluded therein. However, in certain embodimentsthe optimum sensitization will also vary with developer composition;e.g., smaller amounts of chemical sensitization are used when theemulsion is to be developed in p-phenylenediaminecontaining developingcompositions, iodide-containing developing compositions and the like.

The silver halide grainscan be chemically sensitized by any of theaccepted procedures. The silver halide grains can be digested withnaturally active gelatin, sulfur compounds can be added, such as thosedescribed in U.S. Pat. No. 1,574,944 by Sheppard issued Mar. 2, 1926,U.S. Pat. No. 1,623,499 by Sheppard et a1 issued Apr. 5, 1927, and U.S.Pat. No. 2,410,689 by Sheppard issued Nov. 5, 1946, or seleniumcompounds can be used, such as those described in U.S. Pat. No.3,297,447 by McVeigh, U.S. Pat. No. 3,297,446 by 5. Dunn, and the like.

The silver halide grains can also be treated with salts of the noblemetals, such as ruthenium, palladium and platinum. Representativecompounds are ammonium chloropalladate, potassium chloroplatinate andsodium chloropalladite, which are used for sensitizing in amounts belowthat which produces any substantial fog inhibition, as described inSmith and Trivelli, US. Pat. No. 2,448,060 issued Aug. 31, 1948, and asantifoggants in higher amounts, as described in Trivelli and Smith, U.S.Pat. No. 2,566,245 issued Aug. 28, 1951, and U.S. Pat. No. 2,566,263issued Aug. 28, 1951.

The silver halide grains can also be chemically sensitized with goldsalts as described in U.S. Pat. No. 2,399,083 by Waller et al issuedApr. 23, 1946, and U.S. Pat. No. 2,642,361 by Damsehroder et al issuedJune 16, 1953. Suitable compounds are potassium chloraurite, potassiumaurithiocyanate, potassium chloroaurate, auric trichloride and2-aurosulfobenzothiazole methoehloride.

The silver halide grains can also be chemically sensitized with reducingagents, such as stannous salts (Carroll, U.S. Pat. No. 2,487,850 issuedNov. 15, 1949), polyamines such as diethylenetriamine (Lowe et al, U.S.Pat. No. 2,518,698 issued Aug. 15, 1950), polyamines such as spermine(Lowe et al, U.S. Pat. No. 2,521,925 issued Sept. 12, 1950), orbis(B-aminoethyl)sulfide and its water-soluble salts (Lowe et al, U.S.Pat. No. 2,521,926 issued Sept. 12, 1950).

The silver halide grains can also be optically sensitized with cyanineand merocyanine dyes, such as those described in U.S. Pat. Nos.1,846,301 and 1,846,302, both issued Feb. 23, 1932, and US. Pat. No.1,942,854 issued Jan. 9, 1934, all by Brooker; U.S. Pat. No. 1,990,507by White issued Feb. 12, 1935; U.S. Pat. No. 2,112,140 issued Mar. 22,1938, U.S. Pat. No. 2,165,338 issued July 11, 1939, U.S. Pat. No.2,493,747 issued Jan. 10, 1950, and U.S. Pat. No. 2,739,964 issued Mar.27, 1956, all by Brooker et al; U.S. Pat. No. 2,493,748 by Brooker et alissued Jan. 10, 1950; U.S. Pat. No. 2,503,776 issued Apr. 11, 1950, andUS. Pat. No. 2,519,001 issued Aug. 15,1950, both by Sprague; U.S. Pat.No. 2,666,761 by Heseltine et a1 issued Jan. 19, 1954; U.S. Pat. No.2,734,900 by I-Iesel tine issued Feb. 14, 1956; and'U.S. Pat. No.2,739,149

by VanLare issued Mar. 20,1956; and Kodak Limited British Pat.Specification No. 450,958 accepted July 15, 1936.

In certain embodiments where the surface of the grains has beenchemically sensitized at the low end of the specified range, it isdesirable to incorporate iodidereleasing compounds in the silver halideelement or to use a developer containing iodide ions to obtain certaindesired image characteristics. However, as the level of chemicalsensitization is increased, the use of the iodidereleasing compounds oriodide in the developer or emulsion becomes less desirable.

In accordance with this invention, a simple exposure and developmentprocess can be iised to form a positive image. In one embodiment, aphotographic element comprising at least onelayer of a silver halidecomposition as described above can be imagewiseexposed and thendevelopediri the presence of a fogging agent in a silver halide surfacedeveloper. Inanother embodiment, the element can be given a flashoverall exposure during surfacefdefveloprnmt to provide a positiveimage.

It is understood that the term surface developer" encompasses thosedevelopers which will reveal the surface latent image on a silver halidegrain, but will not reveal substantial internal latent image in aninternal image-forming emulsion, and conditions generally used develop asurface-sensitive silver halide emulsion. The surface developers cangenerally utilize any of the silver halide developing agents or reducingagents, but the developing bath or composition is generallysubstantially free of a silver halide solvent (such as watersolublethiocyanates, water-soluble thioethers, thiosulfates, ammonia and thelike) which will crack or dissolve the grain to reveal substantialinternal image. Low amounts of excess halide are sometimes desirable inthe developer or incorporated in the emulsion as halide-releasingcompounds, but high amounts are generally avoided to prevent substantialcracking of the grain, especially with respect to iodidereleasingcompounds.

Typical silver halide developing agents which can be used inthe.developing compositions of this invention include hydroquinones,catechols, aminophenols, 3- pyrazolidones, ascorbic acid and itsderivatives, reductones, phenylenediamines and the like or combinationsthereof. The developing agents can be incorporated in the photographicelements wherein they are brought in contact with the silver halideafter imagewise exposure; however, in certain embodiments they arepreferably employed in the developing bath.

When an overall flash exposure is used during surface development, itcan be of high intensity for a short duration or of low intensity forlonger duration. However, the light flash can precede development incertain embodiments, such as those embodiments where theimagewise-exposed emulsion is first contacted with a stabilizercomposition.

The developing compositions used in the process of this invention canalso contain certain antifoggants and development restrainers, oroptionally they can be incorporated in layers of the photographicelement.

Generally improved results are obtained when the direct-positiveemulsions are processed in the presence of certain antifoggants asdisclosed in U.S. Pat. No. 2,497,917, which is incorporated herein byreference.

Typical useful antifoggants include benzotriazoles, such asbenzotriazole, methylbenzotriazole, ethylbenzotriazole and the like,benzimidazoles such as 6- nitrobenzimidazole, Smitrobenzimidazole andthe like, benzothiazoles such as 5-nitrobenzothiazole,S-methylbenzothiazole and the like, heterocyclic thiones such as1-methyl-2-tetrazoline-5-thione and the like, triazines such as2,4-dimethylamino-6-chloro-5-triazine and the like, benzoxazoles such asethylbenzoxazole and the like, and pyrroles such as 2,5-dimethylpyrroleand the like.

In certain embodiments, good results are obtained when the emulsions areprocessed in the presence of high levels of the antifoggants mentionedabove. When antifoggants such as benzotriazoles are used, good resultscan be obtained when the processing solution contains up to 5 g./l. andpreferably 1 to 3 g./l.; when they are incorporated in the photographicelement, concentrations of up to 1,000 mg./mo le of Ag and preferablyconcentrations of 300 to 500 rng./mole of Ag are employed.

The surface developer referred to herein as Kodak Developer DK-SO isdescribed in the Handbook of Chemistry and Physics, 30th Ed. 1947,Chemical Rub- 7 her Publishing Co., Cleveland, Ohio, p. 2558, and hasthe following composition:

water, about 125 F. (52 C.) 500 cc. sodium sulfitc. desiccated 30.0 g.N-methyl-p-aminophenol sulfate 2.5 g. hydroquinone 2.5 g. sodiummetaborate 10.0 g. potassium bromide 0.5 g.

water to make 1 liter The silver halide emulsions of this invention canbe developed in a silver halide surface developer in the presence of afogging agent to provide good positive images. The fogging agent can beincorporated in at least one layer of the silver halide element, whichlayer is in water-permeable association with the silver halide emulsion,or it can be contacted with said silver halide emulsion by a separatebath or simultaneously with the surface developer composition byincorporating the fogging agent into the developer composition.Generally, the useful fogging agents of this invention are those whichprovide nucleation or fog specks which initiate development of thesilver halide in the unexposed areas before initiating substantialdevelopment in the exposed areas of an internal-image emulsion in asurface developer. Compounds of this type are generally not practicaldeveloping agents by themselves for silver halides and are referred toas selective fogging agents; in some documents they have been referredto generally as silver halide fogging agents or nucleating agents.Typical useful selective fogging agents include hydrazine compounds,reactive N-substituted cycloammonium salts and the like.

In one preferred embodiment of the invention, hydrazines are used as thefogging agent, such as the compounds disclosed in U.S. Pat. No.2,588,982 by Ives issued Mar. 11, 1952, and U.S. Pat. No. 3,227,552 byWhitmore issued Jan. 4, 1966.

In another preferred embodiment, the fogging agents are reactiveN-substituted cycloammonium quaternary salts. Typical useful foggingagents of this type are disclosed in U.S. Pat. No. 3,615,6l5 by Lincolnet a], U.S. Pat. No. 3,719,494 by Kurtz et al issued Mar. 6, 1973, U.S.Pat. No. 3,734,738 by Kurtz et al issued May 22, 1973, and U.S. Pat. No.3,718,470, which are incorporated herein by reference. Generally, thesecompounds can be represented by the formula:

wherein:

1. Z represents the atoms necessary to complete a heterocyclic nucleuscontaining a heterocyclic ring of five to six atoms including thequaternary nitrogen atom, with the additional atoms of said heterocyclicring being selected from carbon, nitrogen, oxygen, sulfur and selenium;

2. j represents a positive integer of from 1 to 2;

3. a represents a positive integer of from 2 to 6;

4. represents an acid anion;

5. R represents a member selected from:

a. a formyl radical, b a radical having the formula:

wherein each of T and T when taken alone, represents a member selectedfrom an alkoxy radical and an alkylthio radical, and T and T when takentogether, represent the atoms necessary to complete a cyclic radicalselected from cyclic oxyacetals and cyclic thioacetals having from fiveto six atoms in the heterocyclic acetal ring, and c. a l-hydrazonoalkylradical; and 6. R represents either a hydrogen atom, an alkyl radical,an aralkyl radical, an alkylthio radical or an aryl radical such asphenyl and naphthyl, and including substituted aryl radicals.

In certain preferred embodiments of this invention, the N-substituted,cycloammonium quaternary salts are those which contain N-substitutedalkyl radicals having the terminal carbon atom substituted with ahydrazono radical, an acyl radical such as formyl radical, an acetylradical or a benzoyl radical, and those which have a dihydroaromaticring nucleus such as, for example, a dihydropyridinium nucleus.

Generally, the fogging agents can be incorporated in at least one layerof the photographic element in waterpermeable association with thesilver halide emulsion or they can be contacted with the emulsion beforeor during development, such as by a pre-bath or incorporating thefogging agent in the developer composition; however, the fogging agentsare preferably located in at least one layer of the element and in ahighly preferred embodiment they are located in the silver halideemulsion layer. Concentrations of at least 0.5 mg. and preferably fromabout to about 1,500 mg. of the subject fogging agents per mole ofsilver in the silver halide emulsion are useful. These ratios areaccording to conventional practice, however, and with either particularreversal emulsions, fogging compounds of varying chemical activity, orvarying processing conditions, more widely varying fogging agentconcentrations can be advantageously used. When the compounds of U.S.Pat. Nos. 3,615,615 or 3,718,470 are used, the concentration of thefogging agent is preferably from 0.5 to 10 mg./mole of Ag whenincorporated in the photographic element and from about 0.1 to about 2g./l. of solution when incorporated in the developer solution.

Typical useful selective fogging agents include 2- methyl-3-[3-(p-sulfophenylhydrazone)propyl1benzothiazolium bromide, hydrazinedihydrochloride, phenylhydrazine hydrochloride, p-methyl sulfonamideethyl phenyl hydrazine, formyl-4-methyl phenyl hydrazide, 3-(2-formylethyl)-2-methylbenzothiazolium bromide,3-(2-acetylethyl)-2-benzylbenzothiazolium bromide,3-(2-acetylethyl)-2-benzylbenzoselenazolium bromide,1,2-dihydro-3-methyl-4-phenyl pyrido[2, l -b]benzothiazolium bromide,4,4'-ethylene bis(1,2-dihydro3- methylpyrido[2,l-b]benzothiazoliumbromide), 2- methyl -3-[(3-p-nitrophenylhydrazono)propyl]naphtho[2,1-d]thiazolium iodide, and the like.

The silver halide emulsions of this invention can be made by any of theprecipitation and ripening procedures used for making silver halidegrains having metal dopants or metal ions occluded therein. Typicalprocedures include single-jet procedures, double-jet procedures,procedures utilizing automatic proportional control means to maintainspecified pAg and pH, proce- 9 dures using ripening agents such asthiocyanates, thioethers and/or ammonia, procedures utilizing anincrease in flow rates as disclosed in wilgus, U.S. Ser. No. 11,838filed Feb. 16, 1970, now abandoned, hot nucleation procedures asdisclosed in Musliner, U.S. Ser. No. 31,351 filed Apr, 23, 1970, nowabandoned, and the like.

The silver halide compositions made for use in the systems ofthisinvention are preferably monodispersed, and in some embodiments arepreferably large-grain emulsions made according to Wilgus, U.S. Ser. No.11,838, which is incorporated herein by reference. The monodispersedemulsions are those which comprise silver halide grains having asubstantially uniform diameter. Generally, in such emulsions, no morethan about by weight, of the silver halide grains smaller than the meangrain size and/or no more than about 5%, by number, of the silver halidegrains larger than the mean grain size vary in diameter from the meangrain diameter by more than about 40%. Preferred photographic emulsionsof this invention comprise silver halide grains, at least 95%, byweight, of said grains having a diameter which is within 40%, preferablywithin about 30%, of the mean grain diameter. Mean grain diameter, i.e.,average grain size, can be determined using conventional methods, e.g.,such as projective area as shown in an article by Trivelli and Smithentitled Empirical Relations between Sensitometric and Size-FrequencyCharacteristics in Photographic Emulsion Series in The PhotographicJournal, Vol. LXXlX, 1939, pp. 330-338. The aforementioned uniform sizedistribution of silver halide grains is a characteristic of the grainsin monodispersed photographic silver halide emulsions. Silver halidegrains having a narrow size distribution can be obtained by controllingthe conditions at which the silver halide grains are prepared using adouble-run procedure. In such a procedure, the silver halide grains areprepared by simultaneously running an aqueous solution of awater-soluble halide, for example, an alkali metal halide such aspotassium bromide, into a rapidly agitated aqueous solution of a silverhalide peptizer, preferably gelatin, a gelatin derivative or some otherprotein peptizer. The pH and the pAg employed in this type of procedureare interrelated. For example, changing one while maintaining the otherconstant at a given temperature can change the size frequencydistribution of the silver halide grains which are formed. However,generally the temperature is about 30 to about 90 C., the pH is up toabout 9, preferably 4 or less, and the pAg is up to about 9.8. Suitablemethods for preparing photographic silver halide emulsions having therequired uniform particle size are disclosed in an article entitled Ia:Properties of Photographic Emulsion Grains, by Klein and Moisar, TheJournal ofPhotographic Science, Vol. 12, 1964, pp. 24225l; an articleentitled The Spectral Sensitization of Silver Bromide Emulsions onDifferent Crystallographic Faces, by Markocki, The Journal ofPhotographic Science, Vol. 13, 1965, pp. 8589; an article entitledStudies on Silver Bromide 8015, Part I. The Formation and Aging ofMonodispersed Silver Bromide $015, by Ottewill and Woodbridge, TheJournal of Photographic Science, Vol. 13, 1965, pp. 98l03; and anarticle entitled Studies on Silver Bromide Sols, Part II. The Effect ofAdditives on the S01 Particles, by Ottewill and Woodbridge, The JournalofPhotographic Science, Vol. 13, 1965, pp. l04l07.

The photographic emulsions and elements described in the practice ofthis invention can contain various colloids alone or in combination asvehicles, binding agents and various layers. Suitable hydrophilicmaterials include both naturally occurring substances such as proteins,for example, gelatin, gelatin derivatives, cellulose derivatives,polysaccharides such as dextran, gum arabic and the like; and syntheticpolymeric substances such as water-soluble polyvinyl compounds likepoly( vinylpyrrolidone), acrylamide polymers and the like.

The described photographic emulsion layers and other layers ofaphotographic element employed in the practice of this invention can alsocontain, alone or in combination with hydrophilic, waterpermeablecolloids, other synthetic polymeric compounds such as dispersed vinylcompounds such as in latex form and particularly those which increasethe dimensional stability of the photographic materials. Suitablesynthetic polymers include those described, for example, in U.S. Pat.No. 3,142,568 by Nottorf issued July 28, 1964; U.S. Pat. No. 3,193,386by White issued July 6, 1965; U.S. Pat. No. 3,062,674 by Houck et alissued Nov. 6, 1962; U.S. Pat. No. 3,220,844 by Houck et al issued Nov.30, 1965; U.S. Pat. No. 3,287,289 by Ream et al issued Nov. 22, 1966;and U.S. Pat. No. 3,411,911 by Dykstra issued Nov. 19, 1968;particularly effective are those water-insoluble polymers or latexcopolymers of alkyl acrylates and methacrylates, acrylic acid,sulfoalkyl acrylates or methacrylates, those which have crosslinkingsites which facilitate hardening or curing, those having recurringsulfobetaine units as described in Canadiam Pat. No. 774,054 by Dykstra,and those described in U.S. Pat. No. 3,488,708 by Smith issued Jan. 6,1970.

The photographic layers and other layers of a photographic elementemployed and described herein can be coated on a wide variety ofsupports. Typical supports include cellulose nitrate film, celluloseester film, poly(vinyl acetal) film, polystyrene film, poly(ethyleneterephthalate) film, polycarbonate film and related films or resinousmaterials, as well as glass, paper, metal and the like. Typically, :aflexible support is employed, especially a paper support, which can bepartially acetylated or coated with baryta and/or an a1phaolefinpolymer, particularly a polymer of an alpha-olefin containing two to 10carbon atoms such as polyethylene, polypropylene, ethylenebutenecopolymers and the like.

The invention may be used with elements designed for color photography,for example, elements containing color-forming couplers such as thosedescribed in U.S. Pat. No. 2,376,679 by Fro hlich et al, U.S. Pat. No.2,322,027 by Jelley et al, U.S. Pat. No. 2,801,171 by Fierke et al, U.S.Pat. No. 2,698,794 by Godowsky, U.S. Pat. No. 3,227,554 by Barr et aland U.S. Pat. No. 3,046,129 by Graham et a1; or elements to be developedin solutions containing colorforming couplers such as those described inU.S. Pat. No. 2,252,718 by Marines et al, U.S. Pat. No. 2,592,243 byCarroll et a1 and U.S. Pat. No. 2,950,970 by Schwan et a1; and infalse-sensitized color materials such as those described in U.S. Pat.No. 2,763,549 by Hanson.

This invention may be used with elements such as described in U.S. Pat.No. 2,716,059 by Yutzy et al; silver salt diffusion transfer systemswherein development of silver halide precedes solution of the silverhalide with processes as described in U.S. Pat. No. 2,352,014 by Rott,U.S. Pat. No. 2,543,181 by Land, US. Pat. No.

3,020,155 by Yackel et al and U.S. Pat. No. 2,861,885 by Land; colorimage-transfer processes such as described in U.S. Pat. Nos. 3,087,817,3,185,567 and 2,983,606 by Rogers, U.S. Pat. No. 3,253,915 by Weyerts etal, U.S. Pat. No. 3,227,550 by Whitmore et al, U.S. Pat. No. 3,227,551by Barr et al, U.S. Pat. No. 3,227,552 by Whitmore, US. Pat. Nos.3,415,644, 3,415,645 and 3,415,646, all by Land, US. Pat. Nos. 2,543,181and 3,635,707, Canadian Pat. No. 674,082, and Belgian Pat. Nos. 757,959and 757,960, both issued Apr. 23, 1971; and imbibition transferprocesses as described in U.S. Pat. No. 2,882,156 by Minsk; all of whichare incorporated herein by reference.

Generally, the image-transfer film units in accordance with thisinvention comprise:

l. a photosensitive element comprising a support having thereon at leastone layer containing a direct-positive silver halide emulsion preferablyhaving associated therewith an image dye-providing material,

2. an image-receiving layer which can be located on a separate supportand superposed or adapted to be superposed on said photosensitiveelement, or preferably can be coated as a layer in the photosensitiveelement,

3. means containing an alkaline processing composition adapted todischarge its contents within said film unit and wherein said film unitcontains a silver halide developing agent and said direct-positivesilver halide emulsion comprises unfogged silver halide grains whichhave metal dopants occluded therein, wherein said grains are chemicallysensitized on the surface thereof with a sulfur compound:

a. to a level which will provide a density of less than 0.25 in KodakDeveloper DK-SO after imagewise exposure when said photosensitivecomposition is coated at a coverage of between about 300 to about 400mg. of silver/ft. and

b. to at least a level which would provide a density of 0.5 usingundoped silver halide grains of the same grain size and halidecomposition when coated, exposed and developed in like manner, and

4. a fogging agent located in said film unit whereby it will be incontact with said photosensitive composition upon discharge of saidprocessing composition.

In highly preferred embodiments, the film units of this inventioncontain a support having thereon a layer containing a blue-sensitiveemulsion having associated therewith a yellow image dye-providingmaterial, a redsensitive silver halide emulsion having associatedtherewith a cyan image dye-providing material, and a greensensitiveemulsion having associated therewith a magenta image dye-providingmaterial, and preferably all of said image dye-providing materials areinitially immobile image dye-providing materials.

The term image dye-providing material as used herein is understood torefer to those compounds which either (1) do not require a chemicalreaction to form the image dye or (2) undergo reactions encountered inphotographic imaging systems to produce an image dye, such as with colorcouplers, oxichromic compounds and the like. The first class ofcompounds is generally referred to as preformed image dyes and includesshifted dyes, etc., while the second class of compounds is generallyreferred to as dye precursors.

The terms "initially diffusible and initially immobile" as used hereinrefer to compounds which are incorporated in the photographic elementand, upon contact with an alkaline processing solution, aresubstantially diffusible or substantially immobile, respectively.

In one preferred embodiment, the silver halide emulsions of theinvention are used in association with immobile image dye-providingcompounds, wherein said compounds undergo oxidation followed, in certaininstances, by hydrolysis to provide an imagewise distribution of amobile image dye. Compounds of this type can be used withdirect-positive emulsions to form negative image records in the exposedphotographic element and will provide a positive image in diffusible dyefor transfer to an image-receiving layer, such as in an image-transferfilm unit. Typical useful compounds of this type are disclosed inCanadian Pat. No. 602,607 by Whitmore et al issued Aug. 2, 1960, U.S.Ser. No. 351,673 by Fleckenstein et al and Ser. No. 351,700 byFleckenstein, both filed Apr. 16, 1973, and U.S. Pat. No. 3,698,897 byGompf et al, U.S. Pat.No. 3,728,113 by Becker et al, U.S. Pat. No.3,725,062 by Anderson et al, U.S. Pat. No. 3,227,552 by Whitmore, U.S.Pat. Nos. 3,443,939, 3,443,940 and 3,443,941, and the like, all of whichare incorporated herein by reference. Where the receiver layer is coatedon the same support with the photosensitive silver halide layers, thesupport is preferably a transparent support, an opaque layer ispreferably positioned between the image-receiving layer and thephotosensitive silver halide layer, and the alkaline processingcomposition preferably contains an opacifying substance such as carbonor a pI-I-indicator dye which is discharged into the film unit between adimensionally stable support or cover sheet and the photosensitiveelement.

In certain embodiments, the cover sheet can be superposed or is adaptedto be superposed on the photosensitive element. The image-receivinglayer can be located on the cover sheet. In certain preferredembodiments where the image-receiving layer is located in thephotosensitive element, a neutralizing layer is located on the coversheet.

A means for containing the alkaline processing solution can be any meansknown in the art for this purpose, including rupturable containerspositioned at the point of desired discharge of its contents into thefilm unit and adapted to be passed between a pair of juxtaposed rollersto effect discharge of the contents into the film unit, frangiblecontainers positioned over or within the photosensitive element,hypodermic, syringes, and the like.

It is known in the art that neutralizing layers containing acidicmaterials, such as polymeric acids, monomeric acids, hydrolyzablematerials and the like, can be positioned within an image-transfer filmunit to effect shutdown of development of silver halide and transfer ofthe image dye-providing substance. Neutralizing layers can also be usedin the film units of the present invention, including acid layerspositioned behind timing layers to delay neutralization of the element,acid layers positioned near the image-receiving layer, acid layers on acover sheet used to distribute the processing composition uniformly overthe photosensitive element, acid layers within the photosensitiveelement, and the like.

The invention can be further illustrated by the following examples.

EXAMPLE 1 Emulsion A: A silver bromide emulsion is prepared by mixingsimultaneously over a period of 28 min. at a temperature of 70 C. equalmolar solutions of silver nitrate and sodium bromide using a controlledsilver halide precipitation technique. Upon completion of theprecipitation, octahedral crystals having a diameter of 0.5 micronresult. The silver bromide grains are chemically sensitized by adding1.7 mg. of sodium thiosulfate/silver mole and 2.5 mg. of potassiumchloroaurate/silver mole and heating for 30 min. at 70 C. The chemicallysensitized grains are further grown in the same precipitationenvironment as the first precipitation for an additional 28 min., suchthat the final crystalline structure results in octahedral grains 0.8micron in diameter.

The emulsion is then split into separate equal portions and chemicallysensitized at the surface of the grain as illustrated in Tables 1 and 2.

Emulsion B: A silver bromide emulsion is prepared similar to Emulsion A,except no chemical sensitization is added internally to the silverhalide grain. The emulsion is then sensitized at the surface as shown inTables 1 and 2.

Emulsion C: A silver bromide emulsion is prepared similar to Emulsion A,except at the completion of the first precipitation, the 0.5-microngrains are chemically sensitized by adding 0.18 mg. of dimethylselenoureaI- silver mole, 2.57 mg. of sodium thiosulfate/silver mole 30and 3.83 mg. of potassium chloroaurate/silver mole and heating for 30min. at 70 C., and then are grown to 0.8 micron as described in EmulsionA and surfacesensitized as described in Table 1.

EXAMPLE 2 The emulsions described in Example 1 are coated on apolyethylene terephthalate film support at 350 mg. of silver/ft. andexposed on a Bausch and Lomb Spectrograph. The exposed coatings are thenprocessed in De- 4O veloper A, an Elon-hydroquinone surface-typedeveloper, and Developer B, a fogging-type developer of the typedescribed in Ives, U.S. Pat. No. 2,563,785. The results as listed inTable l are observed.

EXAMPLE 3 Emulsions A and B, described in Example 1, are coated with 400mg./mole of silver of the fogging agent2-methyl-3[3-(p-sulfophenylhydrazone)propyl]benzothiazolium bromide on afilm support, exposed as described in Example 2 and processed in anElonhydroquinone developer.

Table 2 Surface Emulsion Internal Sensitivity Surface Number Sensitivity(mg/m.) Developer A 1 2 none no image B None 1 (1.4) fogged (2.1) A 1 2I (1.4) good 2 (2.1) reversal image 1 sodium thiosulfate 2 potassiumchloroaurate EXAMPLE 4 A silver bromoiodide emulsion (2.5 mole percentiodide) is prepared by mixing simultaneously, over a period of min. at atemperature of C., equal molar solutions of silver nitrate and halidesalts using a controlled pAg technique. To the precipitation vesselprior to precipitation are added mg. of 1,8-dihydroxy-3,6-dithiaoctane/silver mole. Upon completion of the precipitation,cubic crystals having a diameter of 0.8 micron result. The silverbromoiodide grains are then chemically sensitized by adding 2.0 mg. ofsodium aurous (l) dithiosulfate dihydrate/silver mole. Two moles of thechemically sensitized grains are further grown by adding 1.0 moles ofsilver nitrate and halide salts for 20 min. at 65 C. Prior to the secondprecipitation, 500 mg. of 1,10-dithia-4,7,l3-16-tetraoxacyclooctadecaneTable 1 External Internal Sensitivity Surface Developer A EmulsionNumber Sensitivity (mg./m.) (Density) Fogging Developer B A l 2 Noneless than 0.25 no image B none 1 1.4) above 0.25 fogged 2 (2.1 1 C l 2 31 (L4) less than 0.25 good reversal image 3 (0.1 A l 2 1 (1.4) less than0.25 good reversal image 2 (2.1 A 1 2 2 (2.1 no observable image weakreversal image A 1 2 l (1.4) less than 0.25 moderate reversal image A 12 1 (1.4) less than 025 good reversal image 4 (0.1 A l 2 2 (2.1) lessthan 0.25 weak reversal image l sodium thiosulfate 2 potassiumchloroaurate 3 dimethyl selenourca 4 thioureu dioxide are added to theprecipitation vessel. The final crystalline structure results in cubicgrains 0.9 micron in diameter. The surface of the grains is thenchemically sensitized by adding 1.0 mg. of sodium aurous (I)dithiosulfate dihydrate/silver mole and finished as shown in thefollowing table. To the emulsion are added 400 mg. of2-methyl-[3-(p-sulfophenylhydrazono)propyl1benzothiazoliumbromide/silver mole.

The above finished emulsions are then coated on a film support at 350mg. of silver/ft. and exposed on a Bausch and Lomb Spectrograph. Theexposed coatings are processed in an Elon-hydroquinone developercontaining 50 mg. of S-methyl benzotriazole/liter. The following resultsare observed.

Finish Time Relative Speed Dmax Dmin AD EXAMPLE 5 A halide-coveredemulsion prepared similar to that described in Davey et al, US. Pat. No.2,592,250, having an average grain size of 0.8 micron is coated on apolyethylene terephthalate film support at 350 mg. of silver/ft A secondemulsion prepared as Emulsion A in Example l is surface-sensitized byadding 1.4 mg. of sodium thiosulfate/silver mole and 2.1 mg. ofpotassium chloroaurate/silver mole and coated on a separate polyethyleneterephthalate film support at 350 mg./ft.

To each of the above coated emulsions is added the fogging agent asdescribed in Example 3. After exposing as described in Example 2 andprocessing in Developer A, a speed advantage of 0.6 log E is noticedwith the emulsions of the present invention.

EXAMPLE 6 A silver bromide emulsion is prepared by mixing simultaneouslyover a period of 28 min. at a temperature of 70 C. equal molar solutionsof silver nitrate and sodium bromide. Upon completion of theprecipitation, octahedral crystals having a diameter of 0.5 micronresult. The silver bromide grains are chemically sensitized by adding1.7 mg. of sodium thiosulfate/silver mole and 2.5 mg. of potassiumchloroaurate/silver mole and heating for 30 min. at 70 C. The chemicallysensitized grains are further grown in the same precipitationenvironment as the first precipitation for an additional 28 min., suchthat the final crystalline structure results in octahedral grains 0.8micron in diameter. The emulsion is then chemically sensitized at thesurface of the grains by adding 1.4 mg. of sodium thiosulfate/silvermole and 2.1 mg. of potassium ehloroaurate/silver mole and finished byheating to 65 C. as described in the following table. The emulsions arethen coated on a film support at 350 mg. of silver/ft? and exposed on a16 Bausch and Lomb Spectrograph. The exposed coatings are processed in afogging-type developer (Developer B) of the type described in Ives, USPat. No. 2,563,785. Example 3 if processed in said fogging dcvcloperwhich contains 20 mg./liter of potassium iodide. The results are asfollows:

Example Time of Finish Developer Dmax 1 20765 C. B 1.80 2 0'/65 C. B1.12 3 0/65 C. B Kl 1.88

It can be seen from the above table that adding some iodide to thedeveloper produces improved Dmax in an emulsion which has beenchemically sensitized on the surface to a low level of sensitivity.

EXAMPLE 7 for 15 min. at C. The chemically sensitized grains are furthergrown by adding additional silver nitrate and sodium bromide asdescribed above to obtain a covered-grain emulsion having octahedralgrains having an average diameter of about 1.3 microns. Thecovered-grain emulsion is then chemically sensitized by adding 0.85 mg.of sodium thiosulfate/silver mole and 0.85 mg. of potassiumchloroaurate/silver mole and finished at the times indicated in thefollowing table.

A comparison emulsion (Emulsion E) having a chemically sensitized coreand a chemically sensitized shell is prepared in the same manner asdescribed in Porter et al, US. Pat. No. 3,317,322, Example 1.

The above emulsions are then coated on a film support at 300 mg. ofsilver/ftF, exposed on an Eastman 1B Sensitometer and processed asfollows:

Samples of the above-described coated emulsions are exposed on anEastman 1B Sensitometer and processed in a fogging developer of thefollowing composition for 1 min. at 38 C.

Elon

hydroquinone sodium sulfite sodium hydroxide 5-methylbenzotriazolediglycolic acid 13.4 g sodium phosphate 75.0 g p-methyl sulfonamideethyl phenylhydra 2.0 g

zine distilled water to 1 liter Table 4 Emulsion Finish Time Dmin DmaxAD o '/60C. .18 .29. .11 o l0'/60 c. .18 .48 .30 D 20760" c. .18 1.02.84 n 30'/60 c. .18 2.04 1.86 D 40/60 c. .18 2.42 2.24 E 2s'/70c. 3.023.15 .13

It is apparent from the above tables that the emulsions which have beensufficiently chemically sensitized but have a Dmax in a surfacedeveloper of less than 0.25 produce a more acceptable AD (i.e., at least0.50) in a fogging developer than emulsions which are surface-sensitizedto a level which will provide a high Dmax in a nonfogging surfacedeveloper, i.e., greater than 0.50. It is of interest to note that theDmax areas of Table 3 become the Dmin areas of Table 4.

EXAMPLE 8 The emulsions preferably contain metal dopants occluded in thegrains such as, for example, iridium, osmium, gold, lead, sulfur plusgold, sulfur plus selenium, and the like. The surface of the grains ispreferably chemically sensitized with sulfur, gold, sulfur and gold orgold and reduction sensitization.

A 0.2 cubic-grain internal-image silver bromoiodide monodispersedemulsion (2.5 mole percent iodide) is prepared by adding simultaneouslyan aqueous solution of silver nitrate and an aqueous solution ofpotassium bromide and potassium iodide to a rapidly agitated aqueousgelatin solution containing 100 mg. of potassiumhexachloroiridate/silver mole. The precipitation is carried out in anacidic medium for 60 min. at 70 C. at a pAg of 8.9. A similar emulsionis prepared except potassium hexachloroiridate is omitted and 11.25 mg.of osmium trichloride/silver mole are added. The above emulsions arethen chemically sensitized by adding 33 mg. of sodium thiosulfate/silvermole and 6.6 mg. of potassium chloroaurate/silver mole and heated to 15'at 65 C. The emulsions are coated on a film support at 100 mg.silver/ft, image-exposed on an Eastman 1B Sensitometer and developed inan Elonhydroquinone developer such as Kodak Developer D-l9 for 3 min.During development the film samples are overall flashed for 30 sec.using a l-watt bulb at a distance of 2 ft. Positive images having thefollowing photographic characteristics are observed.

Chemical Sensiti- Chemical Sensitization of Core zation of Shell DmaxDmin iridium none .05 .04 iridium sulfur gold 1.28 .10 osmium none .08.04 osmium sulfur gold 1.19 .22

EXAMPLE 9 The compositions and processes of this invention can beemployed to make improved image-transfer sys-.

18 terns. A film unit adapted to be processed by passing said unitbetween a pair of juxtaposed pressure-applying members is preparedaccording to the following procedure.

A silver bromide emulsion is prepared by mixing simultaneously over aperiod of 50 min. at a temperature of C. equal molar solutions of silvernitrate and sodium bromide using a controlled silver halideprecipitation technique. Upon completion of the precipitation,octahedral crystals having a diameter of 0.9 micron re* sult. The silverbromide grains are chemically sensitized by adding 1.7 mg. of sodiumthiosulfate/silver mole and 2.5 mg. of potassium chloroaurate/silvermole and heating for 15 min. at 70 C. The chemically sensitized grainsare further grown in the same precipitation environment as the firstprecipitation for an additional 40 min., such that the final crystallinestructure results in octahedral grains 1.3 micron in diameter.

The grains are then chemically sensitized on the surface by adding 0.40mg. of sodium thiosulfate/silver mole and 0.40 mg. of potassiumchloroaurate/silver mole and heating for 10 min. at 65 C. The emulsionis divided into three portions and one portion is spectrally sensitizedin the green region of the spectrum, another is spectrally sensitized tothe red region of the spectrum, and another is sensitive only in theblue region of the spectrum.

A multilayer photographic element is then prepared using the aboveemulsion by coating the following layers in order on a transparentcellulose acetate film support:

1. image-receiving layer of methyl-trim-dodecyl ammoniump-toluenesulfonate (22.5 mg./ft. N-nhexadecyl-N-morpholinium ethosulfate(150 mg./ft. and gelatin (743 mg./ft.);

2. light-reflecting layer of TilO (3000 mg./ft.) and gelatin (300mg./ft.

3. opaque scavenger interlayer of l-hydroxy-N-[a-(2,4-di-tert-amylphenoxy)brutyl]-2-naphthamide (100 mg./ft. gelatin (360mg./ft. tricresyl phosphate (50 mg./ft.) and carbon black (300 mg./ft.

4. red-sensitive gelatin-silver bromide emulsion (120 mg. gelatin/ft.and 100 mg. silver/ftF), cyan image-transfer couplerl-hydroxy-4-{4-[a-(3-pentadecylphenoxy)butyramido]phenoxy}-N-methyl-3',5'-dicarboxy-Z-naphthanilide mg./ft. and fogging agentformyl-4-methylphenylhydrazide (0.5 g./mole of silver bromide);

5. scavenger interlayer ofl-hydroxy-N-[a-(2,4-ditert-amylphenoxy)butyl1-2-naphthamide (45 mg./ft.tricresyl phosphate (22 mg./ft. and gelatin (65 mg./ft.

6. green-sensitive gelatin-silver bromide emulsion mg. gelatin/ft. andmg. silver/11. magenta image-transfer coupler l-phenyl-3-(3,5-disulfobenzamido 4-(6-hydroxy-4-pentadecylphenylazo)-5-pyrazolone,dipotassium salt (75 mg./ft. and fogging agent formyl-4-methylphenylhydrazide (0.5 g./mole of silver bromide);

7. scavenger and yellow filter layer of l-hydroxy-N- [a-(2,4-di-tert-amylphenoxy)butyl ]-2-naphthamide (45 mg./ft.), tricresylphosphate (22 mg./ft.), Yellow Carey Lea Silver 10 mgJftF) and gelatin(65 mg./ft.);

8. blue-sensitive gelatin-silver bromide emulsion (100 mg. gelatin/ft.and 100 mg. silver/ft), yellow image-transfer coupler a-pivalyl-a-[4-(N-methylwater 100 ml. benzyl alcohol 0.5 ml. piperidinohexose reductone 0.025 g. S-nitrobenzimidazole 0.005 g. sodium hydroxide1.25 g. 4-amino-N-ethyl-N-B-hydroxyethyl- 1.5 g.

aniline hydroxyethylcellulose 2.5 g

water to 1 liter The processing solution is spread from the pod betweenthe exposed surface of the element and an opaque poly(ethyleneterephthalate) film support coated with a polyacrylic acid layer and apolyvinyl acetate timing layer by passing the transfer sandwich betweena pair of juxtaposed pressure rollers. After 3 min. at about 20 C., amulticolor reproduction of the test object is observed on a whitebackground when viewed through the transparent film support side of theelement. When the above element is compared with an element prepared andprocessed in a similar manner using the emulsion as described in Knottet a1, U.S. Pat. No. 2,592,250, a 0.6 log E increase in photographicspeed is observed.

Similar results can be obtained when using the above prepared silverhalide emulsions in the film units described in U.S. Ser. Nos. 27,990and 27,991, both filed Apr. 13, 1970, and now abandoned, which areincorporated herein by reference.

EXAMPLE A silver bromide emulsion is prepared by mixing simultaneouslyequal molar solutions of silver nitrate and sodium bromide to obtainoctahedral crystals having an average grain size of 0.9 micron. Thesilver bromide grains are chemically sensitized by adding 1.7 mg. ofsodium thiosulfate/silver mole and 1.7 mg. of potassiumchloroaurate/silver mole and finished for 10 min. at 70 C. The grainsare further grown by adding silver nitrate and sodium bromide asdescribed above to 1.3 microns and sensitized by adding 0.85 mg. ofsodium thiosulfate/silver mole and 0.85 mg. of potassiumchloroaurate/silver mole. The emulsion is heated to 70 C. and coated ona paper support at 100 mg. silver/ftf". To the photosensitive layer areadded 107 mg. of the coupler described in Example 2 of U.S. Pat. No.3,476,563 issued Nov. 4, 1969, and a hydrazine fogging agent,formyl-4-methylphenyl hydrazine, at 0.5 g./silver mole as described inWhitmore et a1, U.S. Pat. No. 3,227,550. The photographic element isthen exposed and processed by squeegeeing a pod between samples of thephotosensitive element and a receiving element as described in Example 1of Beavers et a1, U.S. Pat. No. 3,445,228. A positive image in thetransfer dye area having a relative speed of 398 is observed. When ahalide conversion emulsion of the type described in lixample 5 ofWhitmore et a1, U.S.Pat.No. 3,227,550.15 substituted for the instantemulsion and processed as described, a direct-positive image having aspeed of 1001s observed.

20 Similar results are obtained when the hydrazine fogging agent ispresent in the processing pod.

EXAMPLE 11 The direct-positive emulsions of this invention areespecially useful in image-transfer film units wherein thedirect-positive emulsion has associated therewith an immobile imagedye-providing material which releases an image dye as a function ofoxidation.

A silver halide emulsion is prepared as described in Example 9, with theprovision that l the precipitation medium contains 150 mg. of1,l0-dithio-4,7,l3,16-tetraoxacyclooctadecane/silver mole, (2) the pHand pAg during the precipitations are kept constant and (3) the silverhalide grains are surface-sensitized only with sodium thiosulfate.

The emulsion is divided into three portions and one portion isspectrally sensitized in the green region of the spectrum, another isspectrally sensitized in the red region of the spectrum, and another issensitive only in the blue region of the spectrum.

A multilayer photographic element is then prepared using the aboveemulsions by coating the following layers in order on a celluloseacetate film support:

1. image-receiving layer of copoly[styrene-N-benzyl-N,N-dimethyl-N-(3-maleimidopropyl)ammonium v chloride] (200 mg./ft. andgelatin mg./ft.

2. reflecting layer of titanium dioxide (2,000 mg./ft.

and gelatin (200 mg./ft.

3. opaque layer of carbon black (250 mg./ft. and

gelatin (312 mg./ft.

4. Dye Releaser I (65 mg./ft. dissolved in diethyl lauramide at 50mg./ft. and gelatin (100 mg./ft.);

5. red-sensitive, internal-image gelatin-silver chlorobromide emulsion(100 mg. gelatin/ft. and 125 mg. silver/ftF),2,5-di-sec-dodecylhydroquin0ne (25 mg./ft. and nucleating agent formyl4-methylphenylhydrazine (l g./mole of silver);

6. interlayer of gelatin (100 mg./ft. and 2,5-di-secdodecylhydroquinone(50 mg./ft.

7. Dye Releaser II (150 mg./ft. dissolved in diethyl lauramide atmg./ft. and gelatin (175 mg./ft.

8. green-sensitive, internal-image gelatin-silver chlorobromide emulsionmg. gelatin/ft. and mg. silver/ft. 2,5-di-sec-dodecylhydroquinone (5Omg./ft. and nucleating agent formyl-4- methylphenylhydrazine (1 g./moleof silver);

9.interlayer of gelatin (100 mg./ft. and 2,5-di-secdodecylhydroquinone(50 mg./ft.

l0. Dye Releaser III (100 mg./ft. dissolved in diethyl lauramide at 100mg./ft. and gelatin 150 mg./ft.

l l. blue sensitive, intenal-image gelatin silver chlorobromide emulsion(100 mg. gelatin/ft. and 150 mg. silver/ftF),2,5-di-sec-dodecylhydroquinone (50 mg./ft. and nucleating agentformyl-4- methylphenylhydarzine (1 g./mole of silver); and

12. overcoat of gelatin (82.5 mg./ft.

The Dye Releasers I, II and Ill are described in further detail inEleckenstein et al., U.S. Ser. no. 351,673 filed Apr. 16, 1973; thespecific compounds referred to in the examples are as follows:

Dye Releaser 1 cyan dye-releasing:

OH i I CONH(CH )L;O- a

-0 2 C5Hll so cH SO NH N=N N0 Dye Releaser II magenta dye-releasing:

\ CONH(CH )L O c n mu M50 NHSO OCH3 OH HCOCH Dye Releaser III yellowdye-releasing:

OH CONH(CH )L O-'/ 0 11 l t C H NHSO2 5 11 N=N I N CONHCH sodiumhydroxide 40 g.

4-hydroxymethyl-4-methyl-l-phenyl-3- 4 g.

pyrazolidone S-rnethylbenzyltriazole 2.4 g.

potassium iodide 0.01 g.

hydroxyethyl cellulose 25 g.

distilled water to l000 ml.

After 4 min., the element is separated from the opaque sheet, subjectedto a 1-min. acid rinse, fixed for 4 min., washed and dried. Thefollowing sensitometric results are obtained:

Maximum Density Minimum Density Red Green Blue Red

Green Blue Although the invention has been described in considerabledetail with particular reference to certain preferred embodimentsthereof, variations and modifications can be effected within the spiritand scope of the invention.

I claim:

1. In an image-transfer film unit which comprises an image-receivinglayer, at least one layer ofa photo-sensitive composition havingassociated therewith an image dye-providing material, a developingagent, and a processing composition which can be discharged tofacilitate development of said photosensitive composition by passingsaid unit between a pair of juxtaposed pressure-applying members, theimprovement comprising l said photosensitive composition in said filmunit comprising unfogged silver halide grains having metal dopantsoccluded therein, which grains have been chemically sensitized on thesurface thereof (a) to a level which will provide a density of less than0.4 when developed in Kodak Developer DK-SO for 5 minutes at 27C afterimagewise exposure when said photosensitive composition is coated at acoverage of between about 300 to about 400 mg of silver per square footand (b) to at least a level which would provide a density of 0.5 usingundo'ped silver halide grains of the same grain size and halidecomposition when coated, exposed and developed in like manner, and (2) afogging agent located in said film unit whereby it will be in contactwith said photosensitive composition upon discharge of said processingcomposition.

2. A film unit according to claim I wherein said film unit includes arupturable pod within which said fogging agent is located.

3. A film unit according to claim 1 wherein said fogging agent islocated in at least one layer of said film unit in association with saidlayer containing said silver halide grains.

4. A film unit according to claim 1 wherein said film unit comprises atleast three of said silver halide layers wherein the silver halide inone of said layers is spectrally sensitized to the red region of thevisible light spectrum and the silver halide in another layer isspectrally sensitized to the green region of the visible light spectrum.

5. A film unit according to claim 1 wherein said metal dopants arepolyvalent metal ions.

6. A film unit according to claim 1 wherein said metal dopant iscomprised of sulfur and gold.

7. A film unit according to claim 1 wherein said fogging agent is ahydrazine compound.

8. A film unit according to "claim 1 wherein said fogging agent is areactive N-substituted, cycloammonium quaternary salt.

9. A film unit according to claim 1 wherein said image-receiving layeris located in said unit between said photosensitive composition and thesupport for said photosensitive composition.

10. A film unit according to claim 1 wherein said image-receiving layeris coated on a support and is adapted to be superposed on a supportcarrying said photosensitive composition after exposure thereof.

11. A film unit according to claim 1 wherein said metal dopant iscomposed of sulfur and gold and said unfogged silver halide grains arechemically sensitized on the surface thereof with a sulfur compound toobtain said level of surface sensitization.

12. In a process of forming a transfer image, the improvementcomprising:

1. imagewise-exposing a photosensitive element comprising a supporthaving thereon at least one layer of a photosensitive composition havingassociated therewith an initially immobile image dye-providing materialand silver halide grains having metal dopants occluded therein andwherein said halide is predominantly bromide, which grains have beenchemically sensitized on the surface thereof (a) to a level which wouldproduce a density of less than 0.4 after imagewise exposure whendeveloped in Kodak Developer DK-50, provided said emulsion is coated ata coverage of between about 300 to about 400 mg of silver per squarefoot, and (b) to at least a level which would provide a density of 0.5using undoped silver halide grains of the same grain size and halidecomposition when coated, exposed and developed in like manner;

11. treating said photosensitive element with an alkaline processingcomposition, which is a silver halide surface developer, in the presenceof a fogging agent; and thereby Ill. effecting development of each ofsaid exposed silver halide emulsion layers, thus causing selectiveimagewise diffusion of image dye to an imagereceiver layer.

13. A process according to claim 12 wherein said film unit comprises atleast three separate layers, each containing said silver halide emulsionand each having associated therewith an initially immobile imagedyeproviding material.

14. A process according to claim 12 wherein said silver halide grainshave been chemically sensitized on the surface thereof with sulfur-,gold-, or sulfur-andgold-containing compounds.

15. In an image-transfer film unit which comprises an image-receivinglayer, at least one layer containing a photosensitive composition havingassociated therewith an initially immobile image dye-providing material,a developing agent and a processing composition which can be dischargedto facilitate development of said photosensitive composition by passingsaid unit between a pair of juxtaposed pressure-applying members, theimprovement comprising (1) said photosensitive composition in said filmunit being unfogged silver halide grains wherein the halide ispredominantly bromide and which have metal dopants comprised of sulfurand gold occluded therein, wherein said grains are chemically sensitizedon the surface thereof with a sulfur compound (a) to a level which willprovide a density of less than 0.25 in Kodak Developer DK-SO afterimagewise exposure when said photosensitive composition is coated at acoverage of between about 300 to about 400 mg of silver per square footand (b) to at least a level which would provide a density of 0.5 usingundoped silver halide grains of the same grain size and halidecomposition when coated, exposed and developed in like manner, and (2) afogging agent located in said film unit whereby it will be in contactwith said photosensitive composition upon discharge of said processingcomposition.

16. An image-transfer film unit according to claim 15 which comprises atleast three separate layers containing said photosensitive compositionwherein the silver halide of one of said layers is spectrally sensitizedto the red region of the visible light spectrum and has associatedtherewith a cyan image dye-providing material, the silver halide ofanother layer is spectrally sensitized to the green region of thevisible light spectrum and has associated therewith a magenta imagedye-providing material, and the silver halide in another layer issensitive to the blue region of the visible light spectrum and hasassociated therewith a yellow image dye-providing material.

17. An image-transfer process according to claim 16 wherein each of saidimage dye-providing materials is initially immobile and releases apreformed, diffusible image dye as a function of oxidation followed byhydrolysis.

18. An image-transfer film unit according to claim 15 wherein saidimage-receiving layer is coated on the same support as the layerscontaining said photosensitive composition.

19. An image-transfer film unit comprising:

1. a photographic element having thereon:

a. a layer containing a blue-sensitive silver halide emulsion havingassociated therewith an immobile yellow image dye-providing material,

b. a layer containing a green-sensitized halide emulsion havingassociated therewith an immobile magenta image dye-providing material,and

c. a layer containing a red-sensitized silver halide emulsion havingassociated therewith an immobile cyan image dye-providing material,

2. an image-receiving layer,

3. means containing an alkaline processing composition for developingsaid silver halide emulsion layers adapted to discharge its contentswithin said film unit, and

4. a silver halide developing agent located within said film unit,

wherein each of said silver halide emulsions comprises unfogged silverhalide grains having metal dopants occluded therein, which grains havebeen chemically sensitized on the surface thereof:

a. to a level which will provide a density of less than 0.4 whendeveloped in Kodak Developer DK-SO for 5 minutes at 27C after imagewiseexposure when said photosensitive composition is coated at a coverage ofbetween about 300 to about 400 mg of silver/ft and b. to at least alevel which would provide a density of 0.5 using undoped silver halidegrains of the same grain size and halide composition when coated,exposed and developed in like manner, and

5. a fogging agent located in said film unit whereby it will be incontact with said photosensitive composition upon discharge of saidprocessing composition.

20. A film unit according to claim 19 wherein said fogging agent islocated in each of said layers containing said silver halide emulsions.

21. A film unit according to claim 19 wherein each of said layerscontaining said silver halide emulsions has associated therewith abenzotriazole antifoggant.

22. A film unit according to claim 19 wherein said metal dopants arecomprised of sulfur and gold and said immobile image dye-providingmaterials contains a preformed dye moiety.

1. IN AN IMAGE-TRANSFER FILM UNIT WHICH COMPRISES AN IMAGERECEIVINGLAYER, AT LAST ONE LAYER OF A PHOTO-SENSITIVE COMPOSITION HAVINGASSOCIATED THEREWITH AN IMAGE DYE-PROVIDING MATERIAL, A DEVELOPINGAGENT, AND A PROCESSING COMPOSITION WHICH CAN BE DISCHARGED TOFACILITATE DEVELOPMENT OF SAID PHOTOSENSITIVE COMPOSITION BY PASSINGSAID UNIT ETWEEN A PAIR OF JUXTAPOSED PRESSURE-APPLYING MEMBERS, THEIMPROVEMENT COMPRISING (1) SAID PHOTOSENSITIVE COMPOSITION IN SAID FILMUNIT COMPRISING UNFOGGED SILVER HALIDE GRAINS HAVING METAL DOPANTSOCCLUDED THEREIN, WHICH GRAINS HAVE BEEN CHEMICALLY SENSITIZED ON THESURFACE THEREOF (A) TO A LEVEL WHICH WILL PROVIDED A DENSITY OF LESSTHAN 0.4 WHEN DEVELOPED IN KADAK DEVELOPER DK-50 FOR 5 MINUTES AT 27*CAFTER IMAGEWISE EXPOSURE WHEN SAID PHOTOSENSITIVE COMPOITION IS COATEDAT A COVERAGE OF BETWEEN ABOUT 300 TO ABOUT 400 MG OF SILVER PER SQUAREFOOT AND (B) TO AT LEAST A LEVEL WHICH WOULD ROVIDE A DENSITY OF 0.5USING UNDOPED SILVER HALIDE GRAINS OF THE SAME GRAIN SIZE AND HALIDECOMPOSITION WHEN COATED, EXPOSED AND DEVELOPED IN LIKE MANNER, AND (2) AFOGGING AGENT LOCATED IN SAID FILM UNIT WHEREBY IT WILL BE IN CONTACTWITH SAID PHOTOSSENSITIVE COMPOSITION UPON DISCHARGE OF SAID PROCESSINGCOMPOSITION.
 2. A film unit according to claim 1 wherein said film unitincludes a rupturable pod within which said fogging agent is located. 2.an image-receiving layer,
 3. means containing an alkaline processingcomposition for developing said silver halide emulsion layers adapted todischarge its contents within said film unit, and
 3. A film unitaccording to claim 1 wherein said fogging agent is located in at leastone layer of said film unit in association with said layer containingsaid silver halide grains.
 4. A film unit according to claim 1 whereinsaid film unit comprises at least three of said silver halide layerswherein the silver halide in one of said layers is spectrally sensitizedto the red region of the visible light spectrum and the silver halide inanother layer is spectrally sensitized to the green region of thevisible light spectrum.
 4. a silver halide developing agent locatedwithin said film unit, wherein each of said silver halide emulsionscomprises unfogged silver halide grains having metal dopants occludedtherein, which grains have been chemically sensitized on the surfacethereof: a. to a level which will provide a density of less than 0.4when developed in Kodak Developer DK-50 for 5 minutes at 27*C afterimagewise exposure when said photosensitive composition is coated at acoverage of between about 300 to about 400 mg of silver/ft2 and b. to atleast a level which would provide a density of 0.5 using undoped silverhalide grains of the same grain size and halide composition when coated,exposed and developed in like manner, and
 5. a fogging agent located insaid film unit whereby it will be in contact with said photosensitivecomposition upon discharge of said processing composition.
 5. A filmunit according to claim 1 wherein said metal dopants are polyvalentmetal ions.
 6. A film unit according to claim 1 wherein said metaldopant is comprised of sulfur and gold.
 7. A film unit according toclaim 1 whrein said fogging agent is a hydrazine compound.
 8. A filmunit according to claim 1 wherein said fogging agent is a reactiveN-substituted, cycloammonium quaternary salt.
 9. A film unit accordingto claim 1 wherein said image-receiving layer is located in said unitbetween said photosensitive composition and the support for saidphotosensitive composition.
 10. A film unit according to claim 1 whereinsaid image-receiving layer is coated on a support and is adapted to besuperposed on a support carrying said photosensitive composition afterexposure thereof.
 11. A film unit according to claim 1 wherein saidmetal dopant is composed of sulfur aNd gold and said unfogged silverhalide grains are chemically sensitized on the surface thereof with asulfur compound to obtain said level of surface sensitization.
 12. In aprocess of forming a transfer image, the improvement comprising: I.imagewise-exposing a photosensitive element comprising a support havingthereon at least one layer of a photosensitive composition havingassociated therewith an initially immobile image dye-providing materialand silver halide grains having metal dopants occluded therein andwherein said halide is predominantly bromide, which grains have beenchemically sensitized on the surface thereof (a) to a level which wouldproduce a density of less than 0.4 after imagewise exposure whendeveloped in Kodak Developer DK-50, provided said emulsion is coated ata coverage of between about 300 to about 400 mg of silver per squarefoot, and (b) to at least a level which would provide a density of 0.5using undoped silver halide grains of the same grain size and halidecomposition when coated, exposed and developed in like manner; II.treating said photosensitive element with an alkaline processingcomposition, which is a silver halide surface developer, in the presenceof a fogging agent; and thereby III. effecting development of each ofsaid exposed silver halide emulsion layers, thus causing selectiveimagewise diffusion of image dye to an image-receiver layer.
 13. Aprocess according to claim 12 wherein said film unit comprises at leastthree separate layers, each containing said silver halide emulsion andeach having associated therewith an initially immobile imagedye-providing material.
 14. A process according to claim 12 wherein saidsilver halide grains have been chemically sensitized on the surfacethereof with sulfur-, gold-, or sulfur-and-gold-containing compounds.15. In an image-transfer film unit which comprises an image-receivinglayer, at least one layer containing a photosensitive composition havingassociated therewith an initially immobile image dye-providing material,a developing agent and a processing composition which can be dischargedto facilitate development of said photosensitive composition by passingsaid unit between a pair of juxtaposed pressure-applying members, theimprovement comprising (1) said photosensitive composition in said filmunit being unfogged silver halide grains wherein the halide ispredominantly bromide and which have metal dopants comprised of sulfurand gold occluded therein, wherein said grains are chemically sensitizedon the surface thereof with a sulfur compound (a) to a level which willprovide a density of less than 0.25 in Kodak Developer DK-50 afterimagewise exposure when said photosensitive composition is coated at acoverage of between about 300 to about 400 mg of silver per square footand (b) to at least a level which would provide a density of 0.5 usingundoped silver halide grains of the same grain size and halidecomposition when coated, exposed and developed in like manner, and (2) afogging agent located in said film unit whereby it will be in contactwith said photosensitive composition upon discharge of said processingcomposition.
 16. An image-transfer film unit according to claim 15 whichcomprises at least three separate layers containing said photosensitivecomposition wherein the silver halide of one of said layers isspectrally sensitized to the red region of the visible light spectrumand has associated therewith a cyan image dye-providing material, thesilver halide of another layer is spectrally sensitized to the greenregion of the visible light spectrum and has associated therewith amagenta image dye-providing material, and the silver halide in anotherlayer is sensitive to the blue region of the visible light spectrum andhas associated therewith a yellow image dye-providing material.
 17. Animage-transfer process according to claim 16 whereIn each of said imagedye-providing materials is initially immobile and releases a preformed,diffusible image dye as a function of oxidation followed by hydrolysis.18. An image-transfer film unit according to claim 15 wherein saidimage-receiving layer is coated on the same support as the layerscontaining said photosensitive composition.
 19. An image-transfer filmunit comprising:
 20. A film unit according to claim 19 wherein saidfogging agent is located in each of said layers containing said silverhalide emulsions.
 21. A film unit according to claim 19 wherein each ofsaid layers containing said silver halide emulsions has associatedtherewith a benzotriazole antifoggant.
 22. A film unit according toclaim 19 wherein said metal dopants are comprised of sulfur and gold andsaid silver halide grains are sensitized on the surface thereof with asulfur sensitizer.
 23. A film unit according to claim 21 wherein each ofsaid immobile image dye-providing materials contains a preformed dyemoiety.